Isobutane pretreatment in alkylation with ethylene utilizing aluminum chloride hydrocarbon complex, hydrogen chloride and ethyl chloride

ABSTRACT

An alkylation process wherein isoparaffin hydrocarbons are alkylated with olefin hydrocarbons in the presence of an aluminum chloride catalyst to yield alkylated hydrocarbons suitable for use in motor fuels. Such process includes an isoparaffin pretreatment step wherein isoparaffin charge is contacted with spent alkylation catalyst to remove contaminants from the isoparaffin which are reactive with aluminum chloride under alkylation conditions.

United States Patent Prescott et al.

[ 1 ISOBUTANE PRETREATMENT IN [75] Inventors: Gerald F. Prescott, Port Arthur;

Charles T. Lewis, Jr.; William R. Owens, both of Nederland, all of Tex.

[73] Assignee: Texaco, Inc., New York, NY.

[22] Filed: Mar. 18, 1974 [21] Appl. No.: 452,084

Related US. Application Data [63] Continuation of Ser. Nov 263,890. June 19. 1972,

abandoned.

[521 US. Cl. 260/683.57 [51] Int. Cl. C07c 3/56 [58} Field of Search 260/683.53, 683.57

[56] References Cited UNITED STATES PATENTS 2,378,733 6/1945 Sensel Zoo/683.53

J! m 3 N E u 35 a N uozum/u 35 37- Q J/ g cm mrr/A/a L} g 0 za/vi a (an) :2

Jff/Vf mmzmr ALKYLATION WITH ETHYLENE UTILIZING ALUMINUM CHLORIDE HYDROCARBON COMPLEX, HYDROGEN CHLORIDE AND ETHYL CHLORIDE [45] Mar. 25, 1975 2,457,564 12/1948 Kniel 260/683.53 2,463,768 3/1949 Hepp t 260/683.57 2,464,682 3/1949 Hepp 260/683.57

Primary Examiner-Delbert E. Gantz Assistant E.\'aminerG. J. Crasanakis Attorney, Agent, or Firm-Thomas H. Whaley; Carl G. Ries [57] ABSTRACT An alkylation process wherein isoparaffin hydrocarbons are alkylated with olefin hydrocarbons in the presence of an aluminum chloride catalyst to yield 211- kylated hydrocarbons suitable for use in motor fuels. Such process includes an isoparaffin pretreatment step wherein isoparaffin charge is contacted with spent alkylation catalyst to remove contaminants from the isoparaffin which are reactive with aluminum chloride under alkylation conditions.

5 Claims, 2 Drawing Figures PATENTED HARZ 5 I975 sum 2 or 2 1 ISOBUTANE PRETREATMENT IN ALKYLATION WITH ETHYLENE UTILIZING ALUMINUM CHLORIDE HYDROCARBON COMPLEX, HYDROGEN CHLORIDE AND ETHYL CHLORIDE This application is a continuation of application Ser. No. 263,890, filed June 19, 1972, now abandoned.

This application is related to U.S. Pat. application Ser. No. 263,887, filed June 19, 1972, now abandoned and US. Pat. application Ser. No. 263,888, filed June 19, 1972, now abandoned.

BACKGROUND OF THE INVENTION The present invention relates to the alkylation of isoparaffins with olefins to produce branched chain paraffin hydrocarbons. More particularly, the present invention relates to the alkylation of isobutane with ethylene employing an aluminum chloride alkylation catalyst. Specifically, the present invention relates to an improved method for removing impurities from an isobutane charge stream to such an alkylation process, which impurities are reactive with the aluminum chloride catalyst under alkylation conditions. The improved method of the present invention comprises treating an isobutane charge stream with spent aluminum chloridehydrocarbon complex catalyst to remove reactive impurities such as water, mercaptans, etc. from the isobutane stream.

Alkylation of branched chain isoparaffin hyhdrocarbons with olefin hydrocarbons in the presence of an alkylation catalyst is well known. Processes for the alkylation of relatively low molecular weight isoparaffin hydrocarbons such as isobutane, isopentane, etc, with olefin hydrocarbons such as ethylene, propylene, and butylene to produce branched chain hydrocarbons suitable for use in motor fuel are widely practiced in commercial facilities. With the increasing emphasis on removing polluents from automobile motor exhaust, the alkylation of isobutane with ethylene is becoming increasingly more important. The major product in alkylating isobutane with ethylene is 2,3-dimethylbutane which has an unleaded Research Octane Number in excess of 100 and which is particularly useful as a compo nent in automobile motor fuel. Many processes have been developed for the alkylation of isobutane with ethylene to form 2,3dimethylbutane employing aluminum chloride as an alkylation catalyst. References to prior art disclosing such processes include US. Pat. Nos. 3,485,893; 2,814,654; 3,470,264; and 3,513,219. Additional prior art references include Hydrocarbon Processing, Alkylate Ethylene for Motor Fuel, May, l97l,pp. l19l2l; and Hydrocarbon Processing, DIP Alkylation," Sept. 1970, p. 200.

An aluminum chloride catalyzed alkylation reaction of isobutane with ethylene is carried out in the liquid phase under conditions such that a hydrocarbon phase comprising isobutane is maintained in intimate contact with a liquid catalyst phase comprising an aluminum chloride-hydrocarbon complex. Alkylation reaction conditions include temperatures in the range of from about 70-150F., pressures of from about 45-400 psia, and residence times of reactants under alkylating conditions of from about 30 seconds to about 60 minutes. isobutane to ethylene molar ratios employed may be from about 2:l to about :1 and volume ratios of hydrocarbon phase to aluminum chloride-hydrocarbon complex catalyst phase of from about 0.511 to about 1:3 may be employed.

Ethylene charge stocks to such an alkylation process need not be completely pure, and may contain such impurities as propylene, propane, and ethane. Propylene will alkylate substantially completely with isobutane under alkylation reaction conditions normally employed. Propane and ethane however, are unaffected by the alkylation reaction. In continuous alkylation process employing recycle streams of unreacted ethylene, such propane and ethane must be removed from the alkylation process. Propane and ethane are generally removed from an alkylation process by venting as a gas stream. Any unreacted ethylene in admixture with such propane and ethane is also vented and thereby lost to the process. Therefore, it is desirable that a relatively high conversion of ethylene charge be obtained in the alkylation reaction either by obtaining a high ethylene conversion on a one-pass basis or by recycling an ethylene-containing stream to the alkylation reaction.

lsobutane charge may contain impurities such as propane and normal butane, which are not converted in the alkylation process. As isobutane is commonly employed in substantial molar excess to ethylene charge in an alkylation process, it is common practice to recycle an isobutane-containing stream to the alkylation reaction. The impurities, such as propane and the normal butane, if allowed to accumulate in the isobutane recycle stream, would soon reach a concentration sufficient to interfere with the alkylation reaction by diluting the isobutane concentration in the hydrocarbon phase. Therefore, in commercial processes, the isobutane for recycle is commonly treated to separate such impurities as propane and normal butane therefrom.

Aluminum chloride is an effective catalyst to promote alkylation of isobutane with ethylene. Aluminum chloride in the presence of hydrogen chloride and a hydrocarbon liquid reacts to form a viscous, reddish liquid complex of aluminum chloride and hydrocarbon. Aluminum chloride catalyst may be added to the alkylation process as aluminum chloride where upon it will combine with hydrocarbons in the reaction Zone to form a complex. Also, the aluminum chloride may be added to the process as an aluminum chloridehydrocarbon complex prepared in a separate facility. Additionally, the aluminum chloride catalyst may be prepared within the process by passing a mixture of hydrogen chloride and liquid hydrocarbon through a bed of metallic aluminum pellets or shavings. Preferably the liquid hydrocarbon employed to form an aluminum chloride-hydrocarbon complex is selected from aromatic and olefinic hydrocarbons. In the alkylation reaction zone, the aluminum chloride-hydrocarbon complex forms a liquid catalyst phase and the isobutane liquid forms a hydrocarbon liquid phase. Intimate contact between catalyst phase and hydrocarbon phase is maintained by such means as agitation wherein the two liquid phases form an emulsion. Upon completion of the reaction step, the hydrocarbon phase and catalyst phase are separated by techniques well known in the art, such as for example, settling, coalescing, etc.

The catalytic effectiveness of alumminum chloride is enhanced by the presence of relatively small amounts of hydrogen chloride in the alkylation reaction. The hydrogen chloride may be admitted into the alkylation reaction as a gas which dissolves in the catalyst phase or may be generated therein by adding a small amount of water to the catalyst phase, whereupon a small portion ofthe aluminum chloride reacts to form hydrogen chloride. Although hydrogen chloride promotes and increases the effectiveness of aluminum chloride as an alkylation catalyst, the hydrogen chloride also reacts with ethylene to form ethyl chloride. Consequently, a portion of ethylene charge to such an alkylation process is consumed by reaction with the hydrogen'chloride. Under normal reaction conditions the concentration of ethylene in the reaction charge mixture is substantially greater than the concentration of hydrogen chloride. As concentration of hydrogen chloride is increased to promote catalytic activity of the aluminum chloride catalyst, the amount of ethylene consumed by reaction with hydrogen chloride also increases. At relatively low concentrations of hydrogen chloride, the aluminum chloride catalyst is not properly promoted and a substantial proportion of the ethylene passes through the alkylation reaction process without being converted into desirable alkylated hydrocarbon product.

In commercial ethylene alkylation processes, an alkylation reaction effluent mixture is separated into a catalyst phase and a hydrocarbon phase by liquid-liquid separation means. The hydrocarbon phase comprises alkylated hydrocarbons, isobutane, unreacted ethylene, ethyl chloride and undesirable materials including methane, ethane, propane, and normal butane which have entered the process mainly as components of the ethylene and isobutane charge streams. As isobutane is used in the alkylation reaction in substantial molar excess, it is common practice to treat the hydrocarbon effluent from an alkylation reaction in a plurality of fractionation zones to separate a stream comprising isobutane which is recycled within the process to the alkylation reaction zone.

A major portion of the catalyst phase separated from an alkylation reaction effluent is commonly recycled to the alkylation reaction zone for use in alkylating additional amounts of isobutane with ethylene. Aluminum chloride alkylation catalyst in the form of an aluminum chloridehydrocarbon complex gradually loses its catalytic activity as it is recycled within an alkylation process. Accumulation of polymeric hydrocarbons within the catalyst phase serve to reduce the catalytic activity of the aluminum chloride complex. Aluminum hydroxide and other side reaction products which result from reaction of aluminum chloride with impurities such as water, decrease the catalytic activity of the catalyst complex. Consequently, a minor portion of the separated catalyst phase is withdrawn from the alkylation process as spent catalyst to remove by-products from the process. Fresh, make-up aluminum chloride catalyst in added to the alkylation reaction zone to replace the amount of catalyst removed from the process as spent catalyst and to restore catalytic activity to the catalyst phase maintained in the alkylation reaction zone.

Many isobutane streams commonly available as charge stock for an alkylation process contain impurities in addition to such inert impurities as propane and normal butane. Impurities such as butene-l, butene-2, methylpropene, butadiene-l, 3-propyene, butyne-l, sulfur dioxide, and methyl mercaptan are often found is isobutane streams available from petroleum refining processes. Such impurities as these react with the aluminum chloride'catalysts. The reaction of such impurities with aluminum chloride catalyst reduces the catalytic activity, or in some cases, such as the sulfur compounds, may destroy the catalytic effectiveness of the aluminum chloride for alkylation of isobutane with ethylene. Therefore, it is common practice to treat isobutane charge streams to remove such impurities prior to admitting such isobutane streams into the alkylation process. Treating methods such as caustic washing, adsorbing impurities upon adsorbents such as molecular sieves, silica-gel, etc. are well known in the prior art. In addition to the reactive impurities discussed above, water is a common impurity found in isobutane charge streams. Such water may be present in the isobutane as obtained from an outside source or may result from a treating step, such as caustic washing, employed to remove other reactive impurities from the isobutane. It is well known to treat the isobutane to remove water therefrom. Treatment with water adsorbcrs such as silica-gel, bauxite, molecular sieves, etc. is well known in the art. In such treating methods as described above to remove reactive impurities including water fromm the isobutane, the medium employed to treat the isobutane gradually losses its capacity for removing such impurities. Consequently, where treating methods such as caustic washings are employed, the treating medium must be discarded and replaced with fresh treating medium. Where treatment of the isobutane with a solid adsorbent is employed, the adsorbent may be discarded or, in some events, regenerated.

SUMMARY OF THE INVENTION Now according to the method of the present invention, an improved method is disclosed for treating an isobutane charge stream for removal of impurities which are reactive with aluminum chloride, prior to charging such isobutane to an alkylation process catalyzed with aluminum chloride catalyst. Such improved process comprises contacting isobutane, in the liquid phase, with spent aluminum chloride-hydrocarbon complex catalyst phase from an alkylation process for a time and under conditions sufficient to allow reaction of substantially all reactive impurities with aluminum chloride; separating a liquid isobutane stream substantially free of reactive impurities from the contacting step; charging such separated isobutane stream to an alkylation process; and removing from the contacting step an aluminum chloride complex phase comprising spent aluminum chloride complex catalyst and reaction products of aluminum chloride and reactive impurities contained in the isobutane charge stream.

Operating conditions include aluminum chlorideisobutane contact time of from about 0.1 to about 30 minutes, operating temperatures of from about 200F., and operating pressures of from about 45400 psig, sufficient to maintain materials present in the contacting zone in the liquid phase. Preferably, the isobutane and aluminum chloride complex are intimately contacted by such means as agitation, to ensure complete reaction of impurities with aluminum chloride. Aluminum chloride complex and liquid isobutane, upon agitation, may form an emulsion. Such emulsion may be separated into a liquid isobutane phase and an aluminum chloride complex phase by such liquid-liquid separation means as gravity settling, coalescing, etc.

Under such conditions as described above, aluminum chloride from the aluminum chloride complex will react with such impurities as water, dienes, acetylenes, sulfur compounds, and other reactive compounds to form reaction products which are soluble in the aluminum chloride complex phase and substantially insoluble in the liquid isobutane phase. By employing the method of this invention, isobutane treating methods such as caustic washing may be eliminated with the concomitant elimination of spent caustic disposal. Additionally an isobutane dryer for removal of water may be eliminated. With elimination of the dryer the necessity of regenerating adsorbent employed in such dryer is likewise eliminated. These and other advantages will be more fully described in the detailed description of the invention which follows.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 of the drawing is a schematic representation I DETAILED DESCRIPTION OF THE INVENTION Alkylation ofisobutane with ethylene in the presence of aluminum chloride alkylation catalyst is well known. Such alkylation reactions are carried out in the liquid phase at temperatures of from about 70F. to about l50F,, pressures of from about 45 psia, residence times of from about 30 seconds to about 60 minutes, and with molar ratios of isobutane to ethylene of from about 2:1 to about 25:1.

Aluminum chloride under alkylation conditions forms a complex with hydrocarbons which is a heavy reddish liquid substantially insoluble in the liquid bydrocarbon reactants ofthe alkylation reaction mixture. The aluminum chloride alkylation catalyst may be added to the alkylation reaction as aluminum chloride or as an aluminum chloride-hydrocarbon complex. When catalyst is added to the alkylation reaction, as aluminum chloride, it complexes with hydrocarbon in the reaction mixture. Additionally, an aluminum chloride-hydrocarbon complex may be generated within the process by mixing hydrogen chloride and liquid hydrocarbon and contacting this mixture with metallic aluminum in the form of pellets or shavings. The preferred volume ratio ofaluminum chloride-hydrocarbon complex catalyst to liquid hydrocarbon reactants in the alkylation reaction is in the range of from about 0.5:] to about 3:l.

The catalytic activity of aluminum chloride as a catalyst for alkylating isobutane with ethylene may be substantially increased by employing catalyst promoters. In the alkylation reaction mixture, hydrogen chloride in a ratio of hydrogen chloride to ethylene of from about 7 to about 23 pounds of hydrogen chloride per barrel of ethylene is an effective catalyst promoter. However, the hydrogen chloride reacts with a portion of the ethylene reactant to form ethyl chloride, thereby reducing the yield of desirable alkylated hydrocarbons. It has been found, however, that the amount of hydrogen chloride promoter required may be substantially reduced by employing ethyl chloride with hydrogen chloride as alkylation catalysts promoter. The use of ethyl chloride and hydrogen chloride as promoters for aluminum chloride alkylation catalysts is described in more detail in copending application Ser. No. 263,887 filed June I9, 1972. When ethyl chloride is used with hydrogen chloride as catalyst promoter, the amount of hydrogen chloride to effectively promote catalyst activity may be reduced to about I to about 6 pounds of hydrogen chloride per barrel of ethylene. Consequently, the portion of ethylene converted to ethyl chloride by reaction with hydrogen chloride may be substantially reduced. Ethyl chloride from the alkylation reaction effluent may be recycled back to the alkylation reaction for use as catalyst promoter.

As aluminum chloride-hydrocarbon complex and liquid hydrocarbon reactants are substantially immiscible, the alkylation reaction mixture is subjected to severe agitation or mixing such that an emulsion is formed, thereby insuring good contact of the hydrocarbon reactants with the catalyst. An alkylation reaction effluent comprising this hydrocarbon-catalyst emulsion is separated by liquid-liquid separation means, such as gravity settling, centrifugation, coalescence, etc., into a hydrocarbon phase and a catalyst phase. The separated bydrocarbon phase of the alkylation reaction effluent comprises alkylated hydrocarbon, isobutane, unreacted ethylene, ethyl chloride, and impurities including methane, ethane, propane, normal butane, polymer hydrocarbon, and heavy alkylate hydrocarbons. The preferred alkylated hydrocarbon product from the alkylation reaction is 2,3-dimethylbutane which has an unleaded Research Octane Number greater than 100. Side reactions within the alkylation reaction produce less desirable hydrocarbon products including polymer hydrocarbons and heavy alkylate hydrocarbons. Such side reaction product hydrocarbons have relatively low octane numbers and are undesirable components of motor fuels.

In a continuous process, the separated hydrocarbon phase is fractionated to recover alkylated hydrocarbon products, recycle hydrocarbons such as isobutane end ethylene, and to remove impurities including methane, ethane, propane and butane from the alkylation process. Components of the catalyst phase such as aluminum chloride and hydrogen chloride have an adverse effect upon fractionation equipment employed to fractionate the hydrocarbon phase. Such components of the catalyst phase, even in small amounts, lead to corrosion and plugging of fractionation process equipment. The separation process contemplated herein is sufficient to separate essentially all catalyst phase from the hydrocarbon phase of the alkylation reaction effluent. If necessary to ensure complete separation of the catalyst phase, intermediate treating of the separated hydrocarbon phase by such methods as bauxite treating is contemplated prior to fractionation.

It is economically desirable to recycle a major portion of the separated catalyst phase to the alkylation reaction to catalyze alkylation of additional hydrocarbon reactants while discarding, as spent catalyst, only a minor portion of the separated catalyst phase. Such spent catalyst is removed from the alkylation process to remove catalyst degradation products such as aluminum hydroxide and polymeric oils from the alkylation process. Polymer hydrocarbons side reaction products are soluble in the alkylation catalyst complex. An accumulation of polymer hydrocarbon adversely affects the catalytic activity of the alkylation catalyst complex. In addition to such hydrocarbon side reaction products, small amounts of water may be introduced into the alkylation process or be generated therein. Such water reacts with aluminum chloride of the catalyst complex to form hydrogen chloride and aluminum hydroxide. Such aluminum hydroxide accumulates in the catalyst complex phase and reduces the catalytic effectiveness of the aluminum chloride-hydrocarbon complex. Consequently, in a continuous aluminum chloride catalyzed alkylation process wherein aluminum chloridehydrocarbon complex catalyst is recycled for contact with additional hydrocarbon reactants, it is necessary to remove a portion of the used catalyst complex and replace that portion removed with fresh catalyst in order to maintain the desired catalytic activity of the recycled catalyst complex.

According to the present invention, we have discovered that the amount of used catalyst complex which must be removed from an alkylation process is sufficient to react with essentially all reactive impurities found in isobutane streams commonly employed as charge stock to such an alkylation process. The usefulness of such spent catalyst in treating an isobutane charge stream to a continuous alkylation process is demonstrated in the following example.

EXAMPLE 1 An aluminum chloride catalyzed alkylation process for alkylation of isobutane with ethylene is operated to yield 5,000 barrels per day of alkylated hydrocarbon. In such process, isobutane and ethylene, in a weight ratio of about 12:1 isobutane to ethylene are contacted with an aluminum chloride-hydrocarbon complex catalyst phase in a volume ratio of about 1:1 hydrocarbon liquid to catalyst complex under conditions of severe agitation in an alkylation reaction zone. Agitation in the reaction zone is sufficient to maintain the hydrocarbon phase-catalyst complex reaction mixture as an emulsion. Operating conditions within the alkylation reaction zone include reaction mixture residence time of about 30 minutes, a temperature of about 130F., and a pressure of about 265 psig. The alkylation catalyst complex is promoted with about 5.0 pounds of hydrogen chloride per barrel of ethylene charged and about 2l.l pounds of ethyl chloride per pound of hydrogen chloride which hydrogen chloride and ethyl chloride are added directly to the alkylation reaction zone. Under such operating conditions about 86.l percent of ethylene charged to the alkylation reaction zone is converted in the reaction zone. Alkylation reaction zone effluent, comprising an emulsion, is separated by gravity settling into a hydrocarbon phase and a catalyst complex phase. An alkylated hydrocarbon product is recovered from the separated hydrocarbon phase and unreacted isobutane is recovered for recycle to the alkylation reaction zone. A major portion of the separated catalyst complex is returned for contact with additional hydrocarbon reactants in the alkylation reaction zone. In order to maintain the catalytic activity of the catalyst complex a small portion of the separated catalyst complex is removed from the process as spent catalyst and is replaced in the alkylation reaction zone with fresh aluminum chloride complex. A refinery isobutane stream of about 90 volume percent butane purity and containing I parts per million methylmercaptan and 85 parts per million water is charged to such alkylation process at a rate of 4,630 barrels per day.

In the process described above it is found that in order to maintain the catalytic activity of the aluminum chloride complex present in the alkylation reaction zone, it is necessary to add one pound of aluminum chloride in the form of an aluminum chloridehydrocarbon complex, per 32 gallons of C alkylate produced. Spent alkylation catalyst complex is removed from the alkylation process in a volume amount sufficient to allow addition of fresh aluminum chloride complex and to maintain catalyst inventory relatively constant within the process. The amount of aluminum chloride removed from the process in the spent catalyst when replaced at a rate of 1 pound of aluminum chlo ride per 32 gallons of alkylate is 6,562 pounds ofaluminum chloride per day. This weight of aluminum chloride removed from the process is 49.22 pound moles of aluminum chloride per day. Methylmercaptan at a concentration of parts per million in the 4,630 barrels per day of isobutane charge to the alkylation process amounts to 91.18 per day, or 1.90 pound moles per day of methylmercaptan. The reaction of methylmercaptan with aluminum chloride is:

Thus, it can be seen that one mole of aluminum chloride reacts with three moles of methylmercaptan. Consequently, 0.63 moles per day of aluminum chloride are required to react with the 1.90 moles per day of methylmercaptan contained within the isobutane charge stream.

Water in a concentration of parts per million in the 4,630 barrels per day isobutane charge stream amounts to 169 pounds per day, or 9.39 pound moles per day water contained within the isobutane charge stream. The reaction of aluminum chloride with water is:

Thus, it can be seen that one mole of aluminum chloride reacts with three moles of water. Consequently, 3.l3 pound moles per day aluminum chloride are required to react with the water content ofthe isobutane charge stream.

By adding the aluminum chloride requirements for reacting with methylmercaptan and water present in the isobutane charge stream, it can be seen that 3.76 pound moles per day of aluminum chloride are required to remove these reactive impurities from the isobutane charge. As 49.22 pound moles per day aluminum chloride are available for reaction with impurities in the isobutane charge stream, it can be seen that a substantial excess of aluminum chloride may be pro vided for removing such impurities from the isobutane.

In this example spent catalyst from the alkylation process and isobutane make-up are charged to a contacting vessel wherein the isobutane and spent catalyst are contacted at a temperature of about lO0F., a pressure of about 250 psig sufficient to maintain components in the liquid phase, with agitation to form an isobutane-spent catalyst emulsion, for a contact time of isobutane in the contacting vessel of about 5 minutes. Contacting vessel effluent is transferred to a settling vessel wherein a hydrocarbon phase comprising isobutane essentially free of water and methylmercaptan is separated from a spent catalyst phase containing substantially all the Al(OH);r and Al(SH) reaction products formed in the contacting vessel. A major portion of the separated spent catalyst phase from the settling vessel is returned to the contacting vessel to maintain a volume ratio of spent catalyst to isobutane of about 1:1. A minor portion of the spent catalyst phase from the settling vessel is removed in order to maintain inventory of spent catalyst phase as additional spent catalyst from the alkylation process is added to the contacting vessel. Such used spent catalyst phase from the settling vessel may be diposed of or may be regenerated to form aluminum chloride for use as catalyst in the alkylation process.

In order to better explain the process of the present invention, attention is now drawn to the attached drawings. Following is a description of one embodiment of the invention with reference to FIG. 1 of the drawing which is an alkylation process wherein an isobutane charge stream is contacted with spent catalyst in a contacting vessel and wherein treated isobutane is separated from spent catalyst in a separation vessel prior to charging to the alkylation process.

FIG. 2 of the drawing is a schematic representation of an alkylation process wherein isobutane charge to the process is treated with spent aluminum chloride complex catalyst utilizing process vessels employed in the alkylation process. The invention disclosed herein, the scope of which is defined in the appended claims, is not limited in its application to the details ofthe process and arrangement of parts shown and described in FIGS. 1 and 2 of the drawing, since the invention is capable of other embodiments. Obvious variations and modifications ofthe present invention which are within the spirit and scope of the appended claims are considered to be incorporated herein.

In FIG. 1 an isobutane charge stream in line 3] containing reactive impurities such as water, methylmercaptans, dienes, and acetylenes is contacted in contacting zone 32 with spent catalyst from line 33 as will hereinafter be further described, under conditions of intimate mixing to form an isobutane spent catalyst emulsion. Emulsion from contacting zone 32 passes via line 34 into separation zone 35 wherein an isobutane phase substantially free of reactive impurities is separated from a spent catalyst phase. Such separation is accomplished by gravity settling followed by bauxite treating. A minor portion of separated spent catalyst is withdrawn and discarded from separation Zone 35 via line 35t1antl a major portion ofseparatcd spent catalyst is returned via line 57 to contacting zone 32 to maintain therein the desired spent catalyst-isobutane ratio.

Treated isobutane which may contain inert impurities such as propane and normal butane, is transferred from separation zone 35, FIG. 1, via line 36 into depropanizer fractionation zone 37. A minor portion of a recycle hydrocarbon stream (as will hereinafter be described) is also charged to depropanizer zone 37 from line 38. In depropanizer zone 37, treated isobutane stream and recycled hydrocarbon are separated by fractionation into a C, --C;; fraction and a C, fraction. The C. -C;, fraction comprising propane from the treated isobutane stream and methane, ethane, propane, and unreacted ethylene from the portion of the recycled hydrocarbon stream charged to depropanizer 37, is vented therefrom via line 39. The C, stream comprising isobutane, normal butane and ethyl chloride is transferred from depropanizer zone 37 via line 40 to deisobutanizer zone 41. In diesobutanizer zone 41 the C, stream is separated into an isobutane fraction and a butane-ethyl chloride fraction. The normal butaneethyl chloride stream is removed from deisobutanizer zone 41, and thus from the alkylation process, via line 42. Isobutane, substantially free of contaminants. is transferred from deisobutanizer zone 41, via line 43 to alkylation reaction zone 44. Ethylene reactant from line 45, and hydrogen chloride catalyst promoter from line 46, are also charged to alkylation reaction zone 44. Recycle hydrocarbon, from line 47 (as will hereinafter be further described) comprising recycle isobutane, unreacted ethylene and ethyl chloride catalyst promoter is charged to alkylation reaction zone 44. Alkylation catalyst from line 48 (as will hereinafter be fur ther described), comprising recycle aluminum chloride-hydrocarbon complex and fresh aluminum chloride complex catalyst is the final charge to alkylation reaction zone 44. In alkylation reaction zone 44. ethylene and isobutane reactants in the liquid phase are agitated with aluminum chloride-hydrocarbon complex catalyst to form a reaction mixture emulsion, wherein isobutane is alkylated with ethylene to produce alkylated hydrocarbons. Hydrogen chloride and ethyl chloride present in the alkylation reaction zone 44 serve to promote the catalytic activity of aluminum chloridehydrocarbon complex.

Alkylation reaction emulsion from alkylation reaction zone 44, FIG. 1, is transferred via line 49 to separation zone 50. In separation zone 50 the reaction emulsion effluent is separated by gravity settling followed by bauxite treating into a hydrocarbon phase and an aluminum chloride complex phase. A major portion of the aluminum chloride complex phase is removed from separation zone 50 via line 33 at a rate sufficient to remove spent alkylation catalyst from the alkylation process such that the volume of catalyst phase does not increase upon addition of fresh catalyst from line 52 into the process. From line 33, the spent alkylation catalyst passes into cntacting zone 32 for contact with isobutane charge according to the improved method of the present invention hereinabove described.

Separated hydrocarbon phase from separation zone 50, FIG. 1, comprising isobutane, unreacted ethylene, alkylatedhydrocarbons, diluents, including methane, ethane, propane, and normal butane, and ethyl chloride pass via line 53 into debutanizer fractionation zone 54.

Separated hydrocarbon phase in a debutanizer zone 54, FIG. 1, is fractionated into a C alkylate fraction and a recycle hydrocarbon fraction. The C alkylate fraction substantially free of normal butane, which increases the vapor pressure above a desired value, and free of ethyl chloride, which reduces the octane response of alkylate to added alkyl lead compounds, is recovered from debutanizer zone 54 via line 56 for use as a motor fuel blending component. Recycle hydrocarbon fraction is recovered from debutanizer zone 54 via line 55. Such recycle hydrocarbon fraction comprises isobutane, unreacted ethylene, ethyl chloride, and diluents such as methane, ethane, propane and normal butane. A major portion of recycle hydrocarbon fraction is transferred from line 55 through line 47 as a charge stream to alkylation reaction zone 44, as hereinabove described. A minor portion of recycle hydrocarbon fraction is transferred from line 55 via line 38 to depropanizer zone 37, as hereinabove described. The minor portion of recycle hydrocarbon transferred via line 38 is selected such that excessive amounts of C,C;, diluents are removed from the alkylation process via line 39 and excessive amounts ofnormal butane and ethyl chloride are removed from the alkylation process via line 42, as hereinabove described. such that these compounds do not accumulate within the alkylation process to such extent that they interfere with the alkylation reaction.

By following the process described above, isobutane charge containing reactive impurities such as water, mercaptans, dienes, and acetylenes, may be treated with spent aluminum chloride complex alkylation catalyst to remove such reactive compounds therefrom. Subsequently, such treated isobutane may be charged to an alkylation process the efficiency of which is improved by the absence of such reactive compounds in the isobutane charge stream.

FIG. 2 of the drawings is a schematic representation of an alkylation process employing a different embodiment of the present invention. In FIG. 2, isobutane is alkylated with ethylene in the presence of an aluminum chloride-hydrocarbon complex catalyst in alkylation reaction zone 1. Ethylene reactant from line 2 and hydrogen chloride catalyst promoter from line 3 are charged to alkylation zone 1. lsobutane from line 4, as will hereinafter be further described, is charged to alkylation zone 1. Aluminum chloride alkylation catalyst enters alkylation zone 1 via line 5, as will hereinafter be further described. Ethyl chloride catalyst promoter contained in a normal butane-ethyl chloride recycle stream from line 6 as will hereinafter be further described, is charged to alkylation reaction zone 1. In alkylation reaction zone'l, ethylene and isobutane in the liquid phase and aluminum chloride complex catalyst are agitated to form a reaction emulsion wherein isobutane is alkylated with ethylene. Hydrogen chloride and ethyl chloride are employed in the alkylation reaction to promote the catalytic activity ofthe aluminum chloride complex catalyst.

Reaction emulsion from alkylation zone 1, FIG. 2, is transferred via line 7, to primary separation zone 8 wherein the reaction emulsion is separated by gravity settling into a hydrocarbon phase and a catalyst complex phase. A major portion of the catalyst complex phase is transferred from primary separated zone 8 via line 9 and is mixed with fresh aluminum chloride complex, sufficient to maintain the desired catalytic activity of the recycle aluminum chloride complex, from line l0. Recycle aluminum chloride complex is returned to alkylation reaction zone 1 via line 5, as hereinabove described, for contact with additional hydrocarbon reactants.

Separated hydrocarbon phase from primary separation zone 8, FIG. 2, which may contain small amounts of aluminum chloride complex is transferred via line I l to secondary separation zone 12. A minor portion of aluminum chloride complex from separation zone 8 is transferred via line 13 to mixing zone 14. lsobutane charge to the alkylation process, from line 15, containing reactive impurities such as water, mercaptan, sulfur dioxide, dienes, and acetylenes, enters mixing zone 14. Aluminum chloride catalyst complex and isobutane charge are mixed in mixing zone 14 to form an emulsion and such emulsion is transferred via line 16 to secondary separation zone 12. In secondary separation zone 12, aluminum chloride complex is separated from the hydrocarbon phase transferred from the primary separation zone 8 and from the isobutane transferred from mixing zone 14 by gravity separation means followed by bauxite treating to form a second hydrocarbon phase substantially free of aluminum chloride complex and an aluminum chloride complex phase. A major portion of the secondary separation zone aluminum chloride complex phase is removed as spent catalyst via line 17.

The second hydrocarbon phase from secondary separation zone 12 is transferred via line 19 to debutanizer fractionation zone 20, wherein the second hydrocarbon phase is separated into a C alkylate fraction substantially free of normal butane and ethyl chloride and into a C, and lighter fraction. The C alkylate fraction is recovered from debutanizer zone 20 via line 21 for transfer and future use in motor fuel.

The C and lighter fraction recovered from debutanizer zone 20 via line 22 comprises isobutane, unreacted ethylene, ethyl chloride, and diluents including methane, ethane, propane, and normal butane. A portion of the C and lighter fraction is transferred from line 22 into line 6 at a rate sufficient to provide the necessary ethyl chloride for promotion of aluminum chloride complex catalyst in alkylation reaction zone I, as hereinabove described. The remaining portion of the C, and lighter fraction from line 22 passes via line 23 into depropanizer zone 24 wherein said C, and lighter fraction is separated into a C, C fraction and a C, fraction. The C C fraction from depropanizer zone 24 is vented from the alkylation process via line 25 to remove inert diluents from the alkylation process.

The C fraction in depropanizer zone 24, FIG. 2, comprising isobutane, normal butane, and ethyl chloride is transferred via line 26 to deisobutanizer zone 27 wherein said C, fraction is separated into an isobutane fraction and a normal butane-ethyl chloride fraction. From debutanizer zone 27 the normal butane-ethyl chloride fraction is removed from the alkylation process via line 28 to prevent excessive accumulations of such materials within the alkylation process. The isobutane fraction from depropanizer zone 27 is transferred as recycle via line 4 to alkylation reaction zone 1 as hereinabove described.

By following the process described in FIG. 2 above, isobutane may be alkylated with ethylene in the presence of an aluminum chloride catalyst and isobutane charge containing reactive contaminants may be treated with aluminum chloride complex to remove such contaminants from the isobutane prior to charging to the alkylation reaction zone. The advantage of the process as shown in FIG. 2 is that isobutane charge containing such reactive contaminants may be treated with aluminum chloride complex by a method wherein it is necessary only to add a mixing zone 14 and associated piping to the process equipment commonly employed in one configuration of an aluminum chloride catalyzed alkylation process.

From the embodiments of the invention as shown in FIGS. 1 and 2 of the attached drawings and the description of the invention above, it will be evident to those skilled in the art that modifications and variations are possible in an aluminum chloride catalyzed alkylation reaction without departing from the spirit and scope of the invention as set out in the appended claims.

We claim:

1. In an aluminum chloride catalyzed alkylation process wherein isobutane and ethylene are contacted with an aluminum chloride-hydrocarbon complex catalyst and ethyl chloride in an alkylation reaction zone in the liquid phase, under alkylating conditions, and with agitation sufficient to form an emulsion of reactant hydrocarbons and catalyst, wherein ethylene charge to said process contains C range normal paraffin diluents,

wherein fresh isobutane charge to said process contains C -;C, range normal paraffin diluents and impurities which are reactive with aluminum chloride; the improvement which comprises:

a. reacting, in an alkylation reaction zone, an isobutane stream, substantially free of normal paraffin hydrocarbons and impurities which are reactive with aluminum chloride with an ethylene stream containing C -C noral paraffin impurities in the presence of an aluminum chloride-hydrocarbon complex catalyst and hydrogen chloride catalyst activator for production of alkylated hydrocarbons;

b. separating, in a product separation zone, the reaction effluent from said alkylation reaction-zone into a hydrocarbon phase essentially free of aluminum chloride-hydrocarbon complex catalyst and a catalyst phase;

c. recycling a major portion of said catalyst phase from said product separation zone to said alkyla tion reaction zone for said reacting step (a);

d. fractionating, in a debutanizing zone, said hydrocarbon phasc into a C and heavier alkylated hydrocarbon product fraction and a recycle hydrocarbon fraction comprising isobutane with minor amounts of ethyl chloride, C -C normal paraffin hydrocarbons and unreacted ethylene;

, recycling a major portion of said recycle hydrocarbon fraction to said alkylation reaction zone for reaction of said isobutane with said unreacted ethylene in step (a);

. contacting, in a contacting zone, a minor portion of said catalyst phase from said product separation zone with said fresh isobutane charge containing -C range normal paraffin diluents and impurities which reactive with aluminum chloride for conversion of said reactive impurities into com pounds soluble in said catalyst phase;

. separating, in a separation zone, the effluent from said contacting zone into a catalyst phase containing conversion products of said reactive impurities from said fresh isobutane charge and an isobutane phase containing C;,--C normal paraffin impurities and substantially free of said reactive impurities;

h. fractionating, in a depropanizing zone, the isobutane phase from said separation zone and a minor portion of said recycle hydrocarbon fraction from said debutanizing zone into a C,C fraction comprising C -C normal paraffins and a minor portion of said unreacted ethylene and a depropanizing zone bottoms fraction comprising a major portion isobutane and minor amounts of normal butane and ethyl chloride;

i. fractionating, in a deisobutanizing zone, said depropanizing zone bottoms fraction into a butane fraction comprising normal butane and ethyl chloride and an isobutane fraction substantially free of C -C normal paraffin diluents and said reactive impurities; and

j. charging said isobutane fraction from said dcisolwtanizing zone to said alkylation reaction zone as the isobutane stream of step (a).

2. The method of claim I wherein said fresh isobutane charge and said aluminum chloride-hydrocarbon complex are contacted in said contacting zone in the liquid phase at a temperature of from about 60F to about 200F for a period of from about 0.1 to about 30 minutes with agitation sufficient to form an emulsion of isobutane and catalyst for conversion of essentially all reactive impurities in said fresh isobutane charge.

3. The method of claim 2 wherein fresh aluminum chloride-hydrocarbon complex catalyst is added to said catalyst recycle phase to said alkylation reaction zone to maintain a preselected catalyst activity; wherein said minor portion ofaluminum chloride-hydrocarbon complex catalyst phase passed from said product separation zone to said contacting zone is selected to maintain a selected inventory of catalyst in said alkylation reaction zone; wherein a portion of the aluminum chloridehydrocarbon complex phase from said separation zone is recycled with said catalyst phase from said product separation zone to maintain a volume ratio ofisobutane charge to aluminum chloride-hydrocarbon complex of from about 1:1 to about 2:1 in said contacting zone.

4. In an aluminum chloride catalyzed alkylation process wherein isobutane and ethylene are contacted with an aluminum chloride hydrocarbon complex catalyst and ethyl chloride in an alkylation reaction Zone in the liquid phase, under alkylating conditions, and with agitation sufficient to form an emulsion of reactant hydrocarbons and catalyst, wherein ethylene charge to said process contains C C range normal paraffin diluents, wherein fresh isobutane charge to said process contains C C range normal paraffin diluents and impurities which are reactive with aluminum chloride; the im provement which comprises:

a. reacting, in an alkylation reaction zone, an isobutane stream substantially free of said reactive impurities with an ethylene stream containing C -C normal paraffin diluents in the presence of aluminum chloride-hydrocarbon complex catalyst and hydrogen chloride catalyst promoter for production of alkylated hydrocarbons;

b. separating, in a primary separation zone, the reaction effluent from said alkylation reaction zone into a first hydrocarbon phase and a first catalyst phase;

c. recycling, a major portion of said first catalyst phase to said alkylation reaction zone for said reacting step (a);

d. adding fresh aluminum chloride-hydrocarbon complex catalyst to said recycled first catalyst phase to maintain catalyst activity;

e. charging to a mixing zone, a minor portion of said first catalyst phase from said primary separation zone, sufficient to maintain the inventory of catalyst in the alkylation reaction zone;

f. contacting, in said mixing zone, said fresh isobutane charge containing C;,C, range normal paraffin diluents and said reactive impurities with said minor portion of said first catalyst phase for conversion of essentially all said reactive impurities;

g. charging the effluent from said mixing zone and said first hydrocarbon phase from said primary separation zone to a secondary separation zone for separation of said effluent and said first hydrocarbon phase into a second hydrocarbon phase comprising isobutane, unreacted ethylene, (T -C, normal paraffin, ethyl chloride and alkylated hydro carbon, and a second catalyst phase;

h. fractionating, in a debutanizing zone, said second hydrocarbon phase into a C and heavier alkylated hydrocarbon fraction and an isobutane fraction including C C, normal paraffin, unreacted ethylene and ethyl chloride;

zone as a second portion of said isobutane stream to said alkylation reaction zone in step (a).

5. The method of claim 4 wherein said fresh isobutane charge and said minor portion of said first catalyst phase are contacted in said mixing zone in the liquid phase, at a temperature of from about 60F to about 200F for a period of from about 0.1 to about 30 minutes with agitation sufficient to form an emulsion for conversion of essentially all reactive impurities in said UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIN PATENT NO. 3,873,635

DATED 1 March 25, 1975 lNVENTOR(5) I Gerald F. Prescott, Charles '1. Lewis, William R. Owens It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 28, delete [hyhdrocarbons] and insert hydrocarbons therefor.

Column 3, line 51, correct spelling of [ia] to read is.

Column 4, line 18, correct spelling of [fromm] to read from.

Column 5, line 25, insert the phrase to about 400 psia between "about 45 psia" and "residence".

Column 7, line 59, correct [85 parts] to read 185 parts.

Column 8, line 14, insert pounds between "91.18" and "per day".

Column 8 line 17, correct formula [Al (SE 1 to read Al (SH) 3.

Column 9, line 3, correct spelling of [diposed] to read disposed.

Column 9, line 60, correct spelling of [diesobutanizer] to read deisobutanizer.

Column 10, line 33, correct spelling of [cntacting] to read contacting.

Column 12, line 68, correct [C to read [C C3] Column 13, line 9, correct spelling of [noral'] to read normal.

Column 13, line 36, insert the word are between "which" and "reactive".

Signed and Scaled this twenty-third 1)" 0; March I 976 [SEAL] Attest:

RUTH C. MASON C. MARSHALL DANN Arresting Officer Commissioner oj'larents and Trademarks 

1. IN AN ALUMINUM CHLORIDE CATALYZED ALKYLATION PROCESS WHEREIN ISOBUTANE AND ETHYLENE ARE CONTACTED WITH AN ALUMINUM CHLORIDE-HYDROCARBON COMPLEX CATALYST AND ETHYL CHLORIDE IN AN ALKYLATION REACTION ZONE IN THE LIQUID PHASE, UNDER ALKYLATION CONDITIONS, AND WITH AGITATION SUFFICIENT TO FORM AN EMULSION OF REACTANT HYDROCARBONS AND CAATALYST, WHEREIN ETHYLENE CHARGE TO SAID PROCESS CONTAINS C1-C3 RANGE NORMAL PARAFFIN DILUENTS, WHEREIN FRESH ISOBUTANE CHARGE TO SAID PROCES CONTAINS C3-C4 RANGE NORMAL PARAFFIN DILUENTS AND IMPURITES WHICH ARE REACTIVE WITH ALUMINUM CHLORIDE; THE IMPROVEMENT WHICH COMPRISES: A. REACTING IN AN ALKYLATION REACTION ZONE, AN ISOBUTANE STREAM, SUBSTANTIALLY FREE OF NORMAL PARAFFIN HYDROCARBONS AND IMPURITIES WHICH ARE REACTIVE WITH ALUMINUM CHLORIDE WITH AN ETHYLENE STREAM CONTAINING C1-C3 NORAL PARAFFIN IMPURITIES IN THE PRESENCE OF AN ALUMINUM CHLORIDE-HYDROCARBON COMPLEX CATALYST AND HYDROGEN CHLORIDE CATALYST ACTIVATOR FOR PRODUCTION OF ALKYLATED HYDROCARBONS; B. SEPARATING, IN A PRODUCT SEPARATION ZONE, THE REACTION EFFLUENT FROM SAID ALKYLATION REACTION-ZONE INTO A HYDROCARBON PHASE ESSENTIALLY FREE OF ALUMINUM CHLORIDEHYDROCARBON COMPLEX CATALYST AND A CATALYST PHASE; C. RECYCLING A MAJOR PORTION OF SAID CATALYST PHASE FROM SAID PRODUCT SEPARATION ZONE TO SAID ALKYLATION REACTION ZONE FOR SAID REACTION STEP (A); D. FRACTIONATING IN A DEBUTANIZING ZONE, SAID HYDROCARBON PHASE INTO A C5 AND HEAVIER ALKYLATED HYDROCARBON PRODUCT FRACTION AND A RECYCLE HYDROCARBON FRACTION COMPRISING ISOBUTANE WITH MONOR AMOUNTS OF ETHYL CHLORIDE, C1-C4 NORMAL PARAFFIN HYDROCARBONS AND UNREACTED ETHYLENE; E. RECYCLING A MAJOR PORTION OF SAID RECYCLE HYDROCARBON FRACTION TO SAID ALKYLATION REACTION ZONE FOR REACTION OF SAID ISOBUTANE WITH SAID UNREACTED ETHYLENE IN STEP (A); F. CONTRACTING, IN A CONTACTING ZONE, A MINOR PORTION OF SAID CATALYST PHASE FROM SAID PRODUCT SEPARATION ZONE WITH SAID FRESH ISOBUTANE CHARGE CONTAINING C1-C4 RANGE NORMAL PARAFFIN DILUENTS AND IMPURITIES WHICH REACTIVE WITH ALUMINUM CHLORIDE FOR CONVERSION OF SAID REACTIVE IMPURITIES INTO COMPOUNDS SOLUBLE IN SAID CATALYST PHASE; G. SEPARAING, IN A SEPARATION ZONE, THE EFFLUENT FROM SAID CONTACTING ZONE INTO A CATALYST PHASE CONTAINING CONVERSION PRODUCT OF SAID REACTIVE IMPURITIES FROM SAID FRESH ISOBUTANE CHARGE AND AN ISOBUTANE PHASE CONTAINING C3-C4 NORMAL PARAFFIN IMPURITIES AND SUBSTANTIALLY FREE OF SAID REACTIVE IMPURITIES; H. FRACTIONATING, IN A DEPROPANIZING ZONE, THE ISOBUTANE PHASE FROM SAID SEPARATION ZONE AND A MINOR PO ISTION OF SAID RECYCLE HYDROCARBON FRACTION FROM SAID DEBUTANIZING ZONE INTO A C1-C4 FRACTION COMPRISING C1-C3 NORMAL PARAFFINS AND A MINOR PORTION OF SAID UNREACTED ETHYLENE AND A DEPROPANIZING ZONE BOTTOMS FRACTION COMPRISING A MAJOR PORTION ISOBUTANE AND MINOR AMOUNTS OF NORMAL BUTANE AND ETHYL CHLORIDE; I. FRACTIONATING, IN A DEISOBUTANIZING ZONE, SAID DEPROPANIZING ZONE BOTTOMS FRACTION INTO A BUTANE FRACTION COMPRISING NORMAL BUTANE AND ETHYL CHLORIDE AND AN ISOBUTANE FRACTION SUBSTANTIALLY FREE OF C1-C4 NORMAL PARAFFIN DILUENTS AND SAID REACTIVE IMPURITIES; AND J. CHARGING SAID ISOBUTANE FRACTION FROM SAID DEISOBUTANIZING ZONE TO SAID ALKYLATION REACTION ZONE AS THE ISOBUTANE STREAM OF STEP (A).
 2. The method of claim 1 wherein said fresh isobutane charge and said aluminum chloride-hydrocarbon complex are contacted in said contacting zone in the liquid phase at a temperature of from about 60*F to about 200*F for a period of from about 0.1 to about 30 minutes with agitation sufficient to form an emulsion of isobutane and catalyst for conversion of essentially all reactive impurities in said fresh isobutane charge.
 3. The method of claim 2 wherein fresh aluminum chloride-hydrocarbon complex catalyst is added to said catalyst recycle phase to said alkylation reaction zone to maintain a preselected catalyst activity; wherein said minor portion of aluminum chloride-hydrocarbon complex catalyst phase passed from said product separation zone to said contacting zone is selected to maintain a selected inventory of catalyst in said alkylation reaction zone; wherein a portion of the aluminum chloride-hydrocarbon complex phase from said separation zone is recycled with said catalyst phase from said product separation zone to maintain a volume ratio of isobutane charge to aluminum chloride-hydrocarbon complex of from about 1:1 to about 2:1 in said contacting zone.
 4. In an aluminum chloride catalyzed alkylation process wherein isobutane and ethylene are contacted with an aluminum chloride hydrocarbon complex catalyst and ethyl chloride in an alkylation reaction zone in the liquid phase, under alkylating conditions, and with agitation sufficient to form an emulsion of reactant hydrocarbons and catalyst, wherein ethylene charge to said process contains C1-C3 rangE normal paraffin diluents, wherein fresh isobutane charge to said process contains C3-C4 range normal paraffin diluents and impurities which are reactive with aluminum chloride; the improvement which comprises: a. reacting, in an alkylation reaction zone, an isobutane stream substantially free of said reactive impurities with an ethylene stream containing C1-C3 normal paraffin diluents in the presence of aluminum chloride-hydrocarbon complex catalyst and hydrogen chloride catalyst promoter for production of alkylated hydrocarbons; b. separating, in a primary separation zone, the reaction effluent from said alkylation reaction zone into a first hydrocarbon phase and a first catalyst phase; c. recycling, a major portion of said first catalyst phase to said alkylation reaction zone for said reacting step (a); d. adding fresh aluminum chloride-hydrocarbon complex catalyst to said recycled first catalyst phase to maintain catalyst activity; e. charging to a mixing zone, a minor portion of said first catalyst phase from said primary separation zone, sufficient to maintain the inventory of catalyst in the alkylation reaction zone; f. contacting, in said mixing zone, said fresh isobutane charge containing C3-C4 range normal paraffin diluents and said reactive impurities with said minor portion of said first catalyst phase for conversion of essentially all said reactive impurities; g. charging the effluent from said mixing zone and said first hydrocarbon phase from said primary separation zone to a secondary separation zone for separation of said effluent and said first hydrocarbon phase into a second hydrocarbon phase comprising isobutane, unreacted ethylene, C1-C4 normal paraffin, ethyl chloride and alkylated hydrocarbon, and a second catalyst phase; h. fractionating, in a debutanizing zone, said second hydrocarbon phase into a C5 and heavier alkylated hydrocarbon fraction and an isobutane fraction including C1-C4 normal paraffin, unreacted ethylene and ethyl chloride; i. recycling a major portion of said isobutane fraction to said alkylation reaction zone as a first portion of said isobutane stream in step (a); j. fractionating, in a depropanizing zone, a minor portion of said isobutane fraction into a C1-C3 fraction comprising C1-C3 paraffins and said unreacted ethylene, and a C4 fraction comprising isobutane, normal butane and ethyl chloride; k. fractionating, in a deisobutanizing zone, said C4 fraction into an isobutane fraction and a fraction comprising normal butane and ethyl chloride; and l. charging said isobutane from said deisobutanizing zone as a second portion of said isobutane stream to said alkylation reaction zone in step (a).
 5. The method of claim 4 wherein said fresh isobutane charge and said minor portion of said first catalyst phase are contacted in said mixing zone in the liquid phase, at a temperature of from about 60*F to about 200*F for a period of from about 0.1 to about 30 minutes with agitation sufficient to form an emulsion for conversion of essentially all reactive impurities in said fresh isobutane charge. 